Denitrification Process Based On Bioaugmentation And Innovative Bioreactors

With the rapid development of urbanization and industrialization in China,the discharge of various types of wastewater is increasing.In 2015,the State Council approved the Water Pollution Prevention and Control Action Plan,which resulted in a significant improvement in the urban sewage treatment capacity.Some key river basins and regions subsequently established local urban sewage plant pollutant discharge standards.With the exception of TN,all the relevant indicators of water quality can almost always meet the "Surface Water Environmental Quality Standard"(GB 3838-2002)IV standard,and can therefore be referred to as "quasi-IV" standard,and with the emergence of high discharge standards,the concept of ultra-clean discharge emerged.The meaning of quasi-IV in ultra-clean discharge is that all indicators except total nitrogen meet the surface water category IV water.As can be seen,the compliance of total nitrogen discharge has become a technical bottleneck for the upgrading of local urban wastewater treatment plants.The compliance of total nitrogen depends on the removal of nitrate,i.e.the denitrification process.This is because the total nitrogen in the tailwater of most wastewater treatment plants mainly consists of nitrate.In order to improve the efficiency of denitrification and achieve deep denitrification,this study was carried out separately from the bioaugmentation and reactor aspects.In terms of biofortification,glucose and quinoline were used as electron donors respectively,and the two strains of bacteria G and F were used for nitrate reduction through biofortification,and the related mechanism was discussed.In terms of reactor,the Vertical Baffled Bio Reactor(VBBR)developed by our research group was used to conduct small and pilot tests respectively,and the influence of the vertical baffled bioreactor on denitrification rate under different carbon nitrogen ratio conditions was discussed,and the relevant mechanism was also discussed.The main elements of this study include:(1)Two strains of pure bacteria,bacteria G and bacteria F,were screened from the denitrifying sludge acclimated by glucose and quinoline respectively.After morphological observation and 16 S r DNA sequence analysis,the G bacteria were finally identified as Comanonas testosteroni and the H bacteria were identified as Rhodococcus ruber.(2)Biofortification of C.testosteroni can significantly accelerate the denitrification rate of glucose as an electron donor.High throughput sequencing found that the abundance of Nirs gene in Comanonas was increased,thereby increasing the nitrite catalytic reduction capacity and accelerating the overall denitrification degradation rate.(3)Using a typical nitrogen-containing heterocyclic compound,quinoline,as an electron donor for denitrification,the addition of R.ruber to the quinoline-domesticated denitrifying sludge accelerated both the rate of biodegradation and mineralisation of quinoline,and the rate of nitrate and nitrite degradation.Although R.ruber can degrade quinoline alone under anoxic conditions,it does not have a functional role in denitrification itself.R.ruber can release electrons from quinoline to denitrifying bacteria to drive nitrate removal.(4)Complete denitrification can be achieved at a COD/N ratio of 3 using a new VBBR reactor.During the 6 h denitrification process,dissolved COD is almost completely lost within the first 2h,but the carbon source(COD)embedded in the denitrifying sludge still provides an electron donor driving the continued removal of nitrate during the subsequent denitrification process.(5)The VBBR reactor can be well insulated from dissolved oxygen,thus allowing for deep denitrification using the VBBR reactor.